Method and apparatus for pretreating liquid fuel



H. S. HILL April 15, 1952 METHOD AND APPARATUS FOR PRETREATING LIQUIDFUELS v 3 Sheets-Sheet 1 Filed Oct. 12, 1949 JNVENTOR.

37F ir April 1952 H. s. HILL 2,592,568

METHOD AND APPARATUS FOR PRETREATING LIQUID FUELS Filed Oct. 12, 1949 aSheets-Sheet 2 f /2 4 0 42 26 5:9 8 8 4. J 48 M z gmun 12m A... I 7

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H. S. HILL April 15, 1952 METHOD AND APPARATUS FOR PRETREATING LIQUIDFUELS a Sheets-Sheet 5 Filed Oct. 12, 1949 R m. M W 6 a; MG;

Patented Apr. 15, 1952 METHOD AND APPARATUS FOR PRETREAT- ING LIQUIDFUEL Harold S. Hill, Lcckport, N. Y.

Application October 12, 1949, Serial No. 120,908

'19 Claims. 1

This invention relates to a method and apparatus for pretreating liquidfuels, such as liquid fuels derived from petroleum, shale oil and coaland used in oil burning furnaces, gasoline engines, diesel engines andthe like.

This application is a continuation-in-part of my copending applicationfor Electric Heater, Serial No. 35,362, filed June 26, 1948, now PatentNo. 2,511,848.

One of the principal objects of the present invention is to provide sucha method and apparatus which during off periods of demand will segregatethe lighter fractions of the stagnant body of oil retained in the heaterand render these lighter fractions available for immediate withdrawalwhen the oil furnace, gasoline engine or the like again goes intooperation. By this means the lighter and more volatile fractions of thefuel are supplied to the apparatus served each time it is started andoptimum conditions are established both for instantaneous starting andalso for establishing proper operating conditions for the continuedburning of the liquid fuel.

Another object is to provide such a method and apparatus which duringcontinued on periods of the apparatus being served will operate topreheat the liquid fuel to a lower temperature than that which obtainsduring the off periods of demand thereby to preheat the liquid fuel forimproved operation of the apparatus being served without, however,separating the lighter fractions. Such lower preheat temperature duringcontinuation of an on period of operation is desirable as the combustionof the fuel in the equipment using the fuel supplies a large part of theheat necessary for eflicient operation so that less preheating isrequired.

Another object is to provide a preheater which is so'chambered andbafiled as to insure rapid heating of the liquid fuel both during on and01? periods of demand and as to insure the rapid segregation of thelighter fractions during the oil periods.

Another object is to provide such a preheater the wall thicknesses ofcertain parts of which are selected to avoid scorching of the liquidfuel with resultant flaking on of solid products of the liquid fuel andwhich are apt to disrupt the operation of the apparatus served.

Another object of the invention is to provide such a preheater the wallthicknesses of certain parts of which are selected to slow down theapplication of heat when called for and to retain heat in the wallsthereby to level off the on and off periods of the preheater and tomaintain more uniform liquid fuel preheating conditions.

Another object is to provide such a preheater the wall thicknesses ofcertain parts of which are selected to rapidly dissipate the heat in theliquid fuel contained in the preheater thereby to condense any vaporizedlighter fractions and in effect to retain them in the liquid phase whilepation being such as to insure segregation of the lighter fractions ofthe liquid fuel for starting and the heat input being such as to providethe proper temperature rise in the liquid fuel during operation of theapparatus being served.

Another object is to provide such a preheater which can be used tovaporize the liquid fuel if desired.

Another object is to provide a thermostat control which is not subjectto hunting or unnecessarily rapid action, the sensitive parts of thethermostatic control being located in the thicker walls of the preheaterfor this purpose.

Another object is to provide turbulence in the liquid fuel passingthrough the preheater to provide improved heat transfer and to insureunlformity in heating all of the liquid fuel passing therethrough to thesame temperature.

Another object is to provide such a preheater which it made of a minimumnumber of simple sections which can be readily assembled and whenassembled provide the above characteristics without danger of leakageand in which all of the electrical parts are readily available forinspection or repair without opening up the liquid fuel chamber of thepreheater.

Another object is to provide a preheater having its body apertured toreceive testing gages used in setting up and checking the operatingconditions of the preheater.

Another object is to provide such a preheater containing a body ofscreening material which not only serves to retain heat and to break upand filter or screen the liquid fuel but also acts as a catalyst insegregating the lighter, more volatile fractions.

Another object is to provide such a preheater which is economical inconsumption of electrical energy when electrically heated.

Another object is. to provide such a preheater which is simple andinexpensive in construction and which will stand up under conditions ofsevere and constant use without getting out of order or requiringrepairs.

Other objects and advantages will appear from the following descriptionand drawings in which:

Fig. 1 is a top plan view of a preheater for liquid fuel embodying thepresent invention.

Fig. 2 is a side elevational view, viewed from the topof Fig. 1.

Fig. 3 is an end elevational view, the right hand side of Fig. 1.

Figs. 4 and 5 are vertical sections taken on the correspondinglynumbered lines on Fig. 1.

viewed from Fig. 6 is a bottom plan view with parts broken dicatedgenerally at M which latter serves to protect the thermostat and heatingelement terminals and wiring as well as to provide an extension or shelfin securing the bottom plate i3 in position.

, The body section II is shown as being of generally rectangular form inplan, with rounding corners, and as having a comparatively thickmetalbottom l5 and relatively thick integral walls rising from thisbottom and being of somewhat lesser thickness than the bottom l5, theseside walls comprising a front wall It, end walls |8 and Hi and a rearwall 20. This body is formed at its center with a relatively thickintegral dam or weir 2| which extends between the front and rear wallsand 29 and divides the interior of the body into two chambers 22 and 23.

The compartment 23 is used as a tempering chamber in which the incomingoil is initially heated and for this purpose the end wall I9 is providedcentrally with an oil inlet opening 24 adapted to receive an oil supplypipe (not shown) this inlet opening 2 3 being arranged close to thebottom of the chamber 23. Both compartments 22 and 23 also act asdistillation chambers in which the temperature of the oil is raisedabove its initial flash point or lowest temperature at which light endsseparate, and preferably below the fire point or lowest temperature atwhich heated oil gives off vapor that supports continuous combustion,this fire point being usually 10 to F. higher than the initial flashpoint. The purpose of so heating the oil above its initial flash pointis for the purpose of segregating the 'lighter and more volatile ends orfractions. In each chamber 22 and 23 the thick bottom wall I5 isprovided with a series of integral transverse ridges 25 which serve toaccelerate heat transfer to the liquid fuel and also to support a filteror screening body 26, one of such bodies being arranged in each chamber22 and 23.

The dam 2| is also preferably provided on opposite sides of its summitwith a plurality of ridges 28 which tend to provide turbulence in theThe summit of the dam and slightly oil flowing thereover. 2| ispreferably arranged in line with below the top rim of the body II. Thisdam is also provided with a relatively large bore 29 which is openthrough the rear wall of the casing and which is closed or blind at itsfront end. This bore 29 receives the sensitive end of a cylindricalthermostat 39, the terminals of which are exposed at the rear wall ofthe casing and are adapted to connect with wires 3| and 32. This dam isalso preferably provided with a blind bore 33 which is similar to thebore 29 except that it is smaller. This bore is adapted to receive athermometer (not shown) by means of which the operator adjusting orchecking the operation of the heater can determine the actualtemperature of the metal forming the dam 2|. It will be seen that thisdam 2| is in effect a control dam, containing the opening 29 for thethermostat 3B and which controls the temperature of this dam in thecenter of the body of liquid so as to insure the required degree of heattransfer from metal to liquid and so as not to have any excessively hotspots which will scorch the fuel and form carbon. This control dam 2|also has the opening 33 to receive a temperature gage to insure settingof the thermostat 3|] to maintain this proper temperature of the controldam.

The underside of the body is provided with a depending skirt 34 whichextends around all four sides thereof and forms a downward continuationof the side walls of the heater to form a chamber 35 for the heatingelement 38, as hereinafter described. The body is also supported onthree integral legs 38 which form downward continuations or the skirt 34below the end walls is and IQ of the heater.

The cover I2 is generally of convex form having a depending rim 39 whichseats upon a gasket 60 which in turn is seated on the top face of theside walls of the body The cover is preferably firmly secured to thebody around its perimeter by a series of screws 4| which extend throughthe cover into threaded holes provided in the side walls of the bodyAbove the chamber 23 the bottom face of the cover is comparatively flatas indicated at 42, this flat extending beyond the summit of the dam 2iand terminating in a relatively large depending ridge or bead 43 whichextends transversely the full width of the casing and extends to a pointapproximately level with or slightly above the summit of the dam 2|.Beyond this ridge or bead 43 the cover is formed to provide an integraldome M into which the light and more volatile ends or fractions rise andcollect. This dome can be of any suitable form but is shown as having afrusto-conioal portion 45 arranged adjacent the end of the heater and aninclined wall portion 46 rising gradually from a point adjacent thetransverse ridge or bead 43 toward the center of the frusto-conicalportion 35. The underside of the gradually rising wall portion 46 of thedome M is preferably provided on its underside with a pair of transverseridges 45 which serve not only to impede the upward movement of thelight ends of the oil but also to accelerate the transfer of heat fromthese light ends to the cover. To further accelerate the dissipation ofheat from these light ends the dome is preferably provided with anexternal extended fin surface, these fins being shown as vertical fins59 projecting outwardly from the frusto-conical portion 45 of the dome.The summit of this frusto-conical portion 45 of the dome is providedwith a vertical outlet opening 5| adapted to receive a pipe (not shown)leading to the oil burner or other apparatus being served.

Heat is shown as supplied from the heatin with one of the binding posts55 element 35, the other binding element indicated generally at 38 andarranged in the chamber 35 'in contact with or close proxiiiiity' to theunderside of the bottom 15 of the casing. This heating element can be ofany type and heated by steam, exhaust gas or any other medium, and isshown as being'in the form of a metal tube 52 housing an electricalresistance wire 53 separated therefrom by insulating beads 54 and theends of the resistance heating wire 53 being connected with suitablebinding posts 55. The heating element is shown as being of generallyU-shaped form so as to conform to and-be in closely spaced relation withthe skirt 34 of the heater, and at the rear of the heater the ends ofthis resistance heating element 36 are shown as being brought togetherand extending thro ig-h a pair of notches 56 formed in the rear part ofthe skirt 34 and within the area enclosed by the cover section 13.Below-the front Wall 18 the heating element 35 is preferably-supportedby a pair of lugs 58 which project rearwardly from the skirt 34.

In addition, a second pair of supporting lugs 59 are formed integrallywith the portion of the skirt 34 below the front wall l6 of the casing.These lugs are disposed below the lugs 58 and project rearwardly tosupport the front edge of the bottom plate l3. At its rear this plate isprovided with a pair of upwardly projecting bosses 50 each of whichprojects into a corresponding one of the notches 56 and engages thecorresponding end of the heating-element 35 projecting through thisnotch so as to hold the rear part of the heating element firmly inposition.

The rear end of the bottom plate I3 is supported by the side coversection l4 of the heater. This side cover section is in the form of anopen sided box fitted against the rear wall 20 of the body in positionto enclose the end of the thermostat 30 and the binding posts 55 atopposite ends of the heating element 36 and is shown as being secured inposition by a pair of horizontal screws 5! which extend through the backof the cover into threaded holes provided in the rear wall 20 of thebody. To support the rear edge of the bottom plate l3, the bottom wallof this cover I4 is formed to provide a forwardly projecting lip 52which extends under the bottom plate l3 as best shown in Fig. 5 so as tosupport the same, the front edge of this cover plate being supported bythe lugs 59 as previously described.

The wire 32 from the thermostat 30 connects of the heating post beingconnected with a wire 3!. The wires 32 and 3! form the line wires andextend outwardly through an opening 63 in the rear wall of the coversection l4 and through a conventional fitting 64 which is secured to therear wall of the cover section l4 in any suitable manner. It will beunderstood that for safety a conventional fusible link (not shown) canbe included in the electrical circuit housed within the cover sectionl4.

In the operation of the invention for pretreating, say, petroleum fueloil for an oil burning furnace, the furnace is automatically cut intoand out of operation in response to the demand for heat. During offperiods no fuel is called for and the body of liquid fuel in the casingI0 becomes a stagnant or quiescent body. An important feature of theinvention resides in the setting of the thermostat 30 a few degreesabove the initial flash point of the liquid fuel, and preferably, thoughnot necessarily below the fire point or lowest temperature at whichheated oil gives off vapor that supports continuous coma bustion, thisfire point being usually 10 to 159*F. higher than the initial flashpoint. Thus, if the initial flash point of the liquid fuel being usedis, say, 148 F., and the fire point is, say, 160 F., the thermostat 39would be set to cut into operation at 150 F., and to cut out ofoperation at 153 F. This setting of the thermostat is readilyaccomplished by the operator who sets the apparatus, the operatorknowing the flash point and fire point from data supplied to him ordetermining the flash point of the fuel being used for himself and theninserting a thermometer (not shown) in the hole 33 provided in thecontrol dam 2| for this purpose. With such thermometer in, serted in thecontrol dam 2|, the operator can readily set the thermostat 30 to cutinto and out of operation at the temperatures indicated. Ac, cess toboth the open end of the hole 33 and to the thermostat 30 can readily beobtained by removing the two screws 6.! which secure the cover M for thethermostat.

With the thermostat so set it would call for heat during on periods ofthe furnace and ac.- cordingly at the start of the off period of thefurnace, the heating element 35 is energized and heat is being appliedby this element to the relatively thick bottom Wall iii of the casing I9. This energization of the electric heating element continues until thetemperature of the control dam '2] builds up to the assumed 153 F., thequiescent body of fuel in the bottom of the chainbers 22 and 23 alsobeing heated to approximately this temperature. It will particularly benoted that this heat is applied at the bottom of the quiescent body ofliquid fuel by the thick bottom wall I5 and, through conduction throughthe metal, at the sides of the body of liquid fuel from the thickcontrol dam 2i and relatively thick side walls of the casing Hi.

As each particle of the liquid fuel is heated above its flash point, thelighter or more volatile fraction thereof vaporizes and rises in thequiescent body of liquid fuel. On encountering cooler fuel, thisvaporized fraction, .of course, recondenses, but since heat is appliedfrom the sides and bottom of the quiescent body of fuel, the net effectof the vaporization and recondensing of the more volatile fraction orlight ends of the liquid fuel is a migration of the light ends to thetop of the body of liquid fuel. Since the cover, above the chamber 22,is inclined, these lighter ends migrate up into the conical part 45 ofthe dome 44. It will be noted that this conical part of the dome isrelatively thin walled and also is provided with the fins 50 so as torapidly dissipate heat to the atmosphere. Accordingly after entering thedome 44 and contacting its walls the light ends are cooled below theirflash point and hence condense and remain as a segregated body of lightends within the conical dome 44. a

This migration of the lighter ends from the chamber 23 is impeded by therib or baflle 43' under which any article of fuel oil must pass in closeproximity to the heated dam 2| before it can escape to the dome 44. Thisprovides independent distillation action in the two chambers 22 and 23,only the substantially completely distilled lighter ends being permittedto escape from the chamber 23 into the chamber 22.

The upward migration of the lighter ends is also impeded by the screenbodies 26 with which each chamber 22 and 23 is packed. This screeningserves not only to distribute the heat throughout the body of liquidfuel in each-chain ber 22 and 23 and also to act as a catalyst, but alsoserves to prevent on effective convection current, from being set up ineither chamber 22 or 23. Without these screen bodies there would be atendency for the cooled fuel at the top of each chamber to flow down thecenter of the liquid fuel therein with the liquid fuel at the sidesrising to replace this cooled liquid fuel. Such a convection movementcan be of sufficient force to prevent the segregation of the light endsin the dome M and is effectively inhibited by the presence of the screenbodies 26.

. Accordingly during off periods of demand mild distillation actiontakes place which effects a segregation of the light ends or morevolatile fraction in the dome 44. Therefore when the furnace goes intooperation the fuel initially supplied is not only heated to a relativelyhigh temperature but also is more highly volatile than the fuel suppliedto the preheater. Accordingly ignition of this initially supplied fuelat the start of each on period is materially expedited and propercombustion of the fuel for a substantial time on each start is assured.After this starting period the combustion of the less volatile fuelsupplied at a lower temperature presents no problem, proper economy infact demanding that the burner be set to operate with the fuel ofaverage volatility and at a lower preheated temperature. Accordingly thecapacity of the heating element 35'is deliberately selected so as toheat the liquid fuel flowing through the preheater on continuedoperation of the fuel burner to only a fraction of the setting of thethermostat 3B. This is for the reason that during a continued on periodthe combustion of the fuel in the apparatus supplies part of the heatfor efficient operation so that preheating to a lower temperature isrequired. It will also be noted, that the transition from the highinitial temperature of the fuel oil in each on period to the relativelylow running temperature is gradual, this being due to the heat stored inthe relatively thick bottom wall I5, relatively thick side walls andalso the relatively thick control dam 2| of the casing section II.

As long as the on period lasts preheated liquid fuel is supplied by thepreheater and when the demand of the burner is satisfied, the flow ofliquid fuel through the preheater is stopped. Accordingly, the nowquiescent body ofliquid fuel in the preheater is again heated to a fewdegrees above its flash point to again segregate the light ends in thedome 44 for the start of another on period.

It will also particularly be noted that all parts of the heater,particularly the electrical components, are readily accessible. Thus byremoving the screws 6| which attach the rear cover section l4, thissection can be removed to expose the terminals of the thermostat 30 andheating element 36 as well as to expose the end of the blind bore 33 forinsertion of a thermometer to check operation. This removal of the rearcover section l4 also removes the lip 62 from under the bottom plate l3which then drops and can be removed. Dropping the bottom plate l3removes its upstanding lugs 60 from supporting engagement with theterminal ends of the heating element 36 which can therefore be removeddownwardly, the front part thereof being merely supported by the lugs58.

From the foregoing it will be seen that the present invention provides avery simple and efflcient method and apparatus for pretreating liquidfuels which effectively segregates, during off periods, the lighter andmore volatile'fractions of the liquid fuel and renders them available athigh temperature for each start of the fuel burner or other apparatusbeing served. It will also be seen that the method and apparatus iseffective, to the degree desired for efiicient oper ation, duringcontinued running conditions.

I claim:

1. A'preheater for liquid fuels for apparatus having on and off periodsof operation, comprising a casing having an inlet for said liquid fuel,a heater arranged to apply heat at a temperature above the initial flashpoint of said liquid fuel to the lower part only of the body of fuelwithin said casing, and a thin walled, small dome rising from a partonly of the top of said casing and subject to external cooling and intowhich the more volatile fraction distilled by said heater rises andsegregates, the outlet for said casing being from said dome whereby saidmore volatile fraction is supplied by the preheater at the start of eachon period of the apparatus being served.

2. A preheater for liquid fuels for apparatus having on and off periodsof operation, comprising a casing having an inlet for said liquid fueland subject to external cooling, a heater arranged to apply heat at atemperature above the initial flash point of said liquid fuel to thelower part only of said casing, a dome maintained by said externalcooling at a temperature below said initial flash point and into whichthe more volatile fraction distilled by said heater rises andsegregates, the outlet for said casing being from said dome whereby saidmore volatile fraction is supplied by the preheater at the start of eachon period of the apparatus being served, and a body of loose material insaid casing and inhibiting convection currents of the liquid fueltherein.

3. A preheater for liquid fuel for apparatus having on and off periodsof operation, comprising a metal casing having relatively thick bottomand side walls and a relatively thin top wall subject to externalcooling, said casing having an inlet for said fuel, a heater arranged toapply heat to said bottom wall at a temperature above the initial flashpoint of sai dliquid fuel, and a relatively thin walled metal domerising from a part of said top wall and maintained by said externalcooling at a temperature below said initial flash point and into whichthe more volatile fraction distilled by said heater rises andsegregates, the outlet for the casing being from said dome whereby saidmore volatile fraction is supplied by the preheater at the start of eachon period of the apparatus being served.

4. A preheater for liquid fuel for apparatus having on and ofl periodsof operation, comprising a metal casing having relatively thick bottomand side walls and a relatively thin top wall subject to externalcooling, said casing having an inlet for said fuel, a heater arranged toapply heat to said bottom wall at a temperature above the initial flashpoint of said liquid fuel, and a relatively thin walled externally finsurfaced metal dome rising from a part of said top wall and maintainedby said external cooling at a temperature below said initial flash pointand into which the more volatile fraction distilled by said heater risesand segregates, the outlet for the casing being from said dome wherebysaid more volatile fraction is supplied by the preheater at the start ofeach on period of the apparatus being served.

5. A preheater for liquid fuel {or apparatus having on and oif periodsof operation, com- .prising a metal casing having relatively thickbottom and side walls and a relatively thin top wall subject to externalcooling, a plurality of ridges projecting downwardly into said casingfrom said top wall, a plurality of ridges projecting upwardly into saidcasing from said bottom wall, said casing having an inlet for said fuel,a. heater arranged to apply heat to said bottom wall at a temperatureabove the initial flash point of said liquid fuel, and a relatively thinwalled externally fin surfaced metal dome rising from a part of said topwall and maintained by said external cooling at a temperature below saidinitial flash point and into which the more volatile fraction distilledby said heater rises and segregates, the outlet for the casing beingfrom said dome whereby said more volatile fraction is supplied by thepreheater at the start of each on period of the apparatus being served.

6. A preheater for liquid fuel for apparatus having on and off periodsof operation, comprising a casing having at one end an inlet for saidliquid fuel, a transverse control dam across the interior of said casingand dividing said casing into an inlet chamber at said one end of saidcasing and an outlet chamber at the other end thereof, said control dambeing composed of a relatively large mass of metal and having an openingadapted to receive the sensitive parts of a thermostat arranged in oneof said openings, a heater controlled by said thermostat and arranged toapply heat at a temperature above the initial flash point of said liquidfuel to the lower part of the body of fuel within said casing, and adome above said outlet chamber and rising from the corresponding end ofthe top of said casing and into which the light ends distilled by saidheater rise and segregate, the outlet for said casing being from saiddome whereby said light ends are supplied by the preheater at the startof each on period of the apparatus being served.

'7. A preheater for liquid fuel for apparatus having on and off periodsof operation, comprising a casing having at one end an inlet for saidliquid fuel, a transverse control dam across the interior of saidcasing, and dividing said easing into an inlet chamber at said one endof said casing and an outlet chamber at the other end thereof, saidcontrol dam being composed of a relatively large mass of metal andhaving openings adapted to receive the sensitive parts of a thermostatand a thermometer, a thermostat arranged in one of said openings, aheater controlled by said thermostat and arranged to apply heat at atemperature above the initial flash point of said liquid fuel to thelower part of the body of fuel within said casing, a dome above saidoutlet chamber and rising from the corresponding end of the top of saidcasing and into which the light ends distilled by said heater rise andsegregate, the outlet for said casing being from said dome whereby saidlight ends are supplied by the preheater at the start of each on periodof the apparatus being served and a body of loose material in each ofsaid chambers and inhibiting convection currents of the liquid fueltherein.

8. A preheater for liquid fuel for apparatus having on and off periodsof operation, comprising a casing having at one end an inlet for saidliquid fuel, a transverse control dam across the interior of saidcasing, and dividing said casing into an inlet chamber at said one endof said casing and an outlet chamber at the other end,

thereof, a heater arranged. to apply heat at a. temperature above theinitial flash point of said liquid fuel to the lower part of the body offuel within said casing, a dome above said outlet chamber and risingfrom the corresponding end of the top of said casing and into which thelight ends distilled by said heater rise and segregate, the outlet forsaid casing being from said dome whereby said light ends are supplied bythe preheater at the start of each on period of the apparatus beingserved, and a body of loose, highly heat conductive material in each ofsaid chambers and inhibiting convection currents of the liquid fueltherein.

9. A preheater for liquid fuel for apparatus having on and off periodsof operation, comprising a metal casing having at one end an inlet forsaid liquid fuel and having relatively thick bottom and side walls and arelatively thin top wall subject to external cooling, a transverse,relatively thick metal control dam across the interior of said casingand dividing said easing into an inlet chamber at said one end of saidcasing and an outlet chamber at its other end thereof said controldambeing composed of a relatively large mass of metal and having an openingadapted to receive the sensitive parts of a thermostat arranged in oneof said openings, a heater controlled'by said thermostat and arranged toapply heat to said bottom wall at a temperature above the initial flashpoint of said liquid fuel, and a relatively thin walled metal dome abovesaid outlet chamber and rising from the corresponding end of said topwall and maintained by said external cooling at a temperature below saidinitial flash point and into which the light ends distilled by saidheater rise and segregate, the outlet for said casing being from saiddome whereby said light ends are supplied by the preheater at the startof each on period of the apparatus being served.

10. A preheater for liquid fuel for apparatus having on and off periodsof operation, comprising a metal casing having at one end an inlet forsaid liquid fuel and having relatively thick bottom and side walls and arelatively thin top wall subiect to external cooling, a transverse,relatively thick metal dam across the interior of said casing anddividing said easing into an inlet chamber at said one end of saidcasing and an outlet chamber at the other end thereof, a heater arrangedto apply heat to said bottom wall at a temperature above the initialflash point of said liquid fuel, and a relatively th n externally finsurfaced walled metal dome above said outlet chamber and rising from thecorrespondin end of said top wall and maintained by said externalcooling at a temperature below said initial flash point and into whichthe light ends disti led by said heater rise and segre ate, the outletfor said casing being from said dome whereby said light ends aresupplied bythe preheater at the start of each on period of the apparatusbeing served.

11. A preheater for liquid fuel for apparatus having on and off periodsof operation, comprising a metal casing having at one end an inlet forsaid liquid fuel and having relatively thick bottom and side walls and arelatively thin top wall subject to external cooling, a transverse,relatively thick metal dam across the interior of said casing anddividing said casing into an inlet chamber at said one end of saidcasing and an outlet chamber at the other end thereof, a heater arrangedto apply heat to said bottom wall at a temperature above the initialflash point of said liquid fuel, a relatively thin externally finsurfaced walled metal dome above said outlet chamber and rising from thecorresponding end of said top wall and maintained by said external,cooling at a temperature below said initial flash point and into whichthe light ends distilled by said heater rise and segregate, the outletfor said casing being from said dome whereby said light ends aresupplied by the preheater at the start of each on period of theapparatus being .served, and a plurality of transverse ridges projectingdownwardly into said casing from said top wall above said outlet chamberand interposed between the summits of said dome and dam to impede themovement of said liquid fuel along said top wall into said dome.

A preheater for liquid fuel for apparatus having on and off periods ofoperation, comprising a metal casing having at one end an inlet for,said licluid fuel and having relatively thick bottom and side walls anda relatively thin top wall subiect'to external cooling, a plurality ofridges projecting upwardly into said casing from said bottom wall,- atransverse, relatively thick metal :dam across the interior of saidcasing and divid- .tively thin external y fln-surfaced walled metal domeabove said outlet chamber and rising from the corresponding end of saidtop wall and maintained-by said external cooling at a temperature Ibelow said initial flash point and into which the light ends distilledby said heater rise and segregate, the outlet for said casing being fromsaid .dorhe whereby said light ends are supplied by the preheater at thestart of each on period of the apparatus being served and a plurality oftrans= verse ridges projecting downwardly into said casing from said topwall above said outlet chamber and interposed between the summits ofsaid dome and dam to impede the movement of said liquid fuel along saidtop wall into said dome.

' 13. A preheater comprising an enclosed casin having an inlet and anoutlet and having a marginal depending skirt forming a heating elementchamber, an electrical resistance heating element within said chamberand having its terminal ends projecting outwardly through a pair ofupwardly extending notches provided in one side of said depending-skirt,a bottom plate for said heatin .element chamber and projecting under thenotched side of said depending skirt, a lug projecting horizontallyinwardly from the side of said-depending skirt opposite said notches andsupporting the corresponding side of said bottom plate, a housingsection arranged to enclose .the terminal ends of said electricalresistance heating element, means removably securing said housingsection to the exterior of the corresponding side wall of said casing,and a lip projecting horizontally from said housing section under the acorresponding side of said bottom plate to support the same.

14; A preheater comprising an enclosed casing having an inlet and anoutlet and having a marginal depending skirt forming a heating elementchamber, an electrical resistanc heating element within said chamber andhaving its terminal ends projecting outwardly through a pair of upwardlyextending notches provided in one side of said depending skirt, a bottomplate for said heating element chamber and projecting under the notchedside of said depending skirt, a pair of upwardly projecting lugs on saidbottom plate and arranged to project upwardly into said notches tosupport said terminal ends of said electrical resistance heatingelement, a lug projecting horizontally inwardly from the side of saiddepending skirt opposite said. notches and supporting the correspondingside of said bottom plate, a housing section arranged to enclose theterminal ends of said electrical resistance heating element, meansremovably securing said housing section to the exterior of thecorresponding side wall of said casing, and a lip projectin horizontallyfrom said housing section under the corresponding side of said bottomplate to support the same.

15. A. preheater comprising an enclosed casing having an inlet and anoutlet and having a marginal depending skirt forming a heating elementchamber, an electrical resistance heating element within said chamberand having its terminal ends projecting outwardly through a pair ofupwardly extending notches provided in one side of said depending skirt,a lug projecting horizontally inwardly from the side of said dependingskirt opposits said notches and arranged to support the correspondingside of said electrical resistance heating element, a bottom plate forsaid heating element chamber and projecting under the notched side ofsaid depending skirt, a pair of upwardly projecting lugs on said bottomplate and arranged to project upwardly into said notches to support saidterminal ends of said electrical resistance heating element, a lugprojecting horizontally inwardly from the side of said depending skirtopposite said notches and supporting the corresponding side of saidbottom plate, a housing section arranged to enclose the terminal ends ofsaid electrical resistance heating element, means removably securingsaid housing section to the exterior of the corresponding side wall ofsaid casing, and a lip projecting horizontally from said housing sectionunder the corresponding side of said bottom plate to support the same.

, 16. An electric heater for fuel oil or the like. comprising ahorizontally elongated casing having a bottom wall, an enclosing sidewall and a top wall, an oil inlet pipe extending through said casing anddischarging oil into one end of said casing near the bottom thereof, atransverse central partition in said casing and having its oppositevertical edges secured to opposite longitudinal parts of the side wallof said casing and having opposite horizontal bottom edges secured tothe bottom wall of said casing to provide a central dam across theinterior of said casing and rising a substantial distance above saidinlet, an electrical heating element arranged on the side of said damremote from said oil and in heat exchange relation therewith, and an oiloutlet pipe extending through said casing and having its outlet arrangedadjacent said top wall at the end of said casing opposite said oil inletpipe.

17. An electric heater for fuel oil or the like, comprising ahorizontally elongated casing having a bottom wall, an enclosing sidewall and a top wall, an oil inlet pipe extending through said casing anddischarging oil into one end of said casing near the bottom thereof, atransverse central partition in said casing and having its oppositevertical edges secured to opposite longitudinal parts of the side wallof said casing and having opposite horizontal bottom edges secured tothe bottom wall of said casing to provide a central dam across theinterior of said casing and rising a substantial distance above saidinlet, an electrical heating element arranged on the side of said damremote from said oil and in heat exchange relation therewith, said topwall of said casing being formed at the end opposite said oil inlet pipeto provide a dome rising from the top wall of said casing at the endthereof opposite said oil inlet pipe, and an oil outlet pipe extendingthrough said casing and having its inlet arranged within the spaceprovided by said dome.

18. The method of pretreating liquid fuels having volatile fractions andsupplied to combustion apparatus at intervals determined by the demandon such'apparatus. which comprises confining a body of said fuel toprovide a stagnant body thereof during oif periods of demand, dividingsaid body into a plurality of connected units to provide a sponge-likebody in which convection currents are inhibited, heating the lower partonly of said body to a temperature above the initial flash point of saidfuel during such ofi period of demand to cause the more volatilefraction thereof to migrate to the top of said body, cooling the top ofsaid body during said off period of demand to condense and segregatesaid more volatile fraction in the top of said body, supplying the fuelto said apparatus from said top of said body whereby said segregatedmore volatile fraction is supplied to said apparatus at the beginning ofeach on period of demand, and supplying fuel to said body at a placeremote from the place where said more volatile fraction is so suppliedto said apparatus.

19. The method of pretreating liquid fuels having volatile fractions andsupplied to combustion apparatus at intervals determined by the demandon such apparatus, which comprises confining a body of said fuel toprovide a stagnant body thereof during off periods of demand, dividingsaid body into a plurality of connected units to provide a sponge-likebody in which convection currents are inhibited, heating the lower partonly of said body to a temperature above the initial flash point of saidfuel and below the fire point thereof during such off period of demandto cause the more volatile fraction thereof to migrate to the top ofsaid body, cooling the top of said body during said off period of demandto condense and segregate said more volatile fraction in the top of saidbody, supplying the fuel to said apparatus from said top of said bodywhereby said segregated more volatile fraction is supplied to saidapparatus at the beginning of each on period of demand, and supplyingfuel to said body at a place remote from the place where said morevolatile fraction is so supplied to said apparatus.

HAROLD S. HILL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,474,524 Garrigan Nov. 20, 19231,562,910 Nook Nov. 24, 1924 1,564,681 Kercher Dec. 8, 1925 1,671,993McTarnahan June 5, 1928 1,678,885 Thomas July 31, 1928 1,861,877 QuillJune 7, 1932 2,010,331 Starrick Aug, 6, 1935 2,099,018 Kennedy Nov. 16,1937 2,240,059 Thoresen Apr. 29, 1941 2,275,689 Shepperd et al. Mar. 10,1942 2,373,084 Morgan et al. Apr. 3, 1945 2,394,868 Morgenier Feb. 12,19 16

